Reports emerged today that warplanes had arrived in the UK's Akrotiri airbase in Cyprus, but De Larrinaga does not believe these would be used against Syria.

"The Akrotiti base could play a supporting role to any military action, but it's highly unlikely that manned aircraft would be involved at this point - although it's possible the UK could support the US by monitoring airspace."

De Larrinaga, the magazine's Europe Editor, said the chances of western military action are increasing and strikes could occur "quickly" after a decision was made.

"The likelihood of small scale, precision strikes using Tomahawk cruise missiles has significantly increased since Britain, France and the US essentially accused Assad of using chemical weapons," he said.

Submarines would likely be deployed in eastern Mediterranean waters or in the Gulf.

De Larrinaga added that airstrikes could be possible "to a limited degree" within Syria using stand-off weapons, without entering Syrian airspace, but cruise missiles remained "the far most likely option".

Parliament is being recalled on Thursday for MPs to discuss the issue, although De Larrinaga says military action would not get UN backing.

"UN Security Council-endorsed military action is a no-go because Russia and China would veto it. It could be a US-led coalition, or possibly a NATO-endorsed mission," he said.

In 2011, the UK carried out strikes on Libya two days before Parliamentary approval was sought, although there had been a UN resolution endorsing a no fly-zone.